Gear pumps often include a housing or plate that holds a set of intermeshing gears. As the gears turn, fluid moves between the gear teeth and the housing and is expelled out the pump due to the intermeshing of the gears. The gears are attached to shafts that run axially from the gear faces, and these shafts run on one or more bearing surfaces.
Gear pumps are employed in a variety of industrial applications, including the pumping of liquid (molten) polymer. As will be understood, in polymer pumping applications, shear degradation of the polymer can occur in the journal bearings associated with the drive gear and the driven gear(s). As a result, reintegration of the degraded material into the flow stream is undesirable, and thus, the material must be removed from the pump after it passes through the bearings. Current approaches result in incomplete removal and/or result in material leakage to the environment, which is undesirable.
In some cases the degraded material is removed by venting high pressure zones at the outboard ends of the pump bearings—through the pump end plates—to a lower pressure region. This results in the degraded material being drawn through the end plates to the lower pressure region where it can be collected. In other cases positive pumping spiral grooves have been provided on a drive shaft extension. As the drive shaft rotates the grooves pump the degraded material away from the bearings and out to the environment. Weepage of media past the shaft bearing has been controlled using a packing seal to throttle the flow rate through the bearing.
Handling and processing of the material once it has been evacuated from the pump is difficult. If simply released to the environment, the degraded polymer will continue to build up on or near the pump until it is mechanically removed. If released to a closed system, a packing seal is still often used around the drive shaft and this packing seal requires periodic mechanical removal of the polymer which builds up over time.
Thus, there is a need for a drainage arrangement that enables continuous removal and collection of degraded polymer, and which eliminates the need for periodic cleaning of degraded polymer from pump surfaces and surrounding surfaces.